1. Field of the Invention
The present invention relates to semiconductor devices. In particular, the present invention relates to programmable LSIs and semiconductor devices including the programmable LSIs. Further, the present invention relates to electronic devices including the semiconductor devices.
2. Description of the Related Art
Programmable LSIs show flexibility in a reduction in development period and a change in design specification as compared to conventional application specific integrated circuits (ASIC) and gate arrays, which is advantageous. Programmable LSIs are widely used in semiconductor devices.
A programmable LSI includes, for example, a plurality of logic elements and wirings between the logic elements. When the functions of the logic elements are changed, the function of the programmable LSI can be changed. The logic element is formed using, for example, a look-up table or the like. The look-up table performs arithmetic processing based on setting data on an input signal so that the input signal is used as an output signal. Here, the setting data is stored in storage elements that correspond to the logic elements. In other words, the look-up table can perform different arithmetic processing in accordance with the data stored in the storage elements. Thus, the functions of the logic elements can be specified when specific setting data is stored in the storage elements.
The setting data or the like of the look-up table is referred to as configuration data. In addition, the storage elements that correspond to the logic elements and store the configuration data are referred to as configuration memories. Further, storage of the configuration data in the configuration memory is referred to as configuration. In particular, rewrite (refresh) of the configuration data stored in the configuration memory is referred to as re-configuration. The circuit structure of the programmable LSI can be changed into a circuit structure suitable for a user's request when desired configuration data is produced (programmed) and configuration is performed.
The programmable LSI generally performs configuration (static configuration) under the condition that the operation of a semiconductor device including the programmable LSI is stopped. In contrast, a technique for performing configuration (dynamic configuration) when the semiconductor device operates in order to further exploit the features of the programmable LSI has attracted attention.
As a method for performing dynamic configuration, Patent Document 1 discloses a method in which a dynamic random access memory (DRAM) is provided separately from a configuration memory and configuration data to be written to the configuration memory is stored in the DRAM. The configuration memory is formed using a static random access memory (SRAM). Patent Document 1 shows a programmable LSI for performing configuration in a short time by reading configuration data from the DRAM and writing the configuration data to the SRAM that is the configuration memory.